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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    //利用async和awaitf封装Ajax函数
    function ajaxfuc() {
      return new Promise((resolve, reject) => {
        let xhr = new XMLHttpRequest()
        xhr.open('Get', 'https://api.apiopen.top/getJoke')
        xhr.send()
        xhr.onreadystatechange = (() => {
          if (xhr.readyState === 4) {
            if (xhr.status >= 200 && xhr.status < 300) {
              resolve(xhr.response)
            } else {
              reject(x.status)
            }
          }
        })
      })
    }
    async function mainajax() {
      try {
        let res = await ajaxfuc()
        console.log(res)
      } catch (error) {
        console.log(error)
      }

    }
    mainajax()
  </script>

</body>

</html>